1. Field of the Invention
The present invention relates to a control device for a vehicle AC (alternating current) generator and, more particularly, relates to a control device in which at least a part can be shared even when electrical configuration positions of field coils of AC generators are different.
2. Description of the Related Art
FIG. 13 is a configuration diagram showing a known vehicle AC generator system. In the drawing, when an internal combustion engine (not shown in the drawing) is started up, a rotor (having a field coil 102) of an AC generator (hereinafter, referred to as a “generator”) is driven via a belt (not shown in the drawing). The field coil 102 is connected to terminals e and f via a slip ring and a brush (not shown in the drawing). With the driving of the rotor, an AC output voltage generated by a three phase armature coil 101 (on the stator side) is rectified by a three phase full wave rectifier 103. ADC (direct current) voltage (DC output voltage) rectified by the rectifier 103 charges a battery 120 connected to the rectifier 103 and supplies a power of 14V to an electric load 130. Incidentally, the armature coil 101, the field coil 102, and the rectifier 103 constitute a generator 100.
Reference numeral 105 denotes a switching element, for example, a power semiconductor switching element which is configured by a MOSFET (metal oxide semiconductor field effect transistor). The switching element 105 is connected in series to the field coil 102. A DC voltage of the rectifier 103 or the battery 120 is applied to a series body of the switching element 105 and the field coil 102 and ON/OFF control of the switching element 105 is performed; accordingly, a field current of the field coil 102 is controlled. 104 denotes a reflux diode; and when the switching element 105 is turned off, the field current due to residual energy in the field coil 102 refluxes through the reflux diode 104.
A control unit 110 performs ON/OFF control of the switching element 105 connected in series to the field coil 102, controls the field current flowing through the field coil 102, and controls an output voltage generated by the armature coil 101 to be a predetermined value. The reflux diode 104, the switching element 105, and the control unit 110 constitute a control device 108 for a vehicle AC generator. The vehicle AC generator system of FIG. 13 shows an electrical configuration position in which the field coil 102 is on the high potential side (high side) and the switching element 105 of the control device 108 is on the low potential side (low side) of a load (field coil 102). Incidentally, a vehicle AC generator system of a similar configuration is disclosed in, for example, Japanese Unexamined Patent Publication No. H3-45200.
FIG. 14 is a configuration diagram showing other known vehicle AC generator system. Incidentally, the same reference numerals as those shown in the specification and accompanying drawings represent identical or equivalent portions and their description will not be repeated. In FIG. 14, a description will be made on portions that are different from FIG. 13. A field coil 102 is connected to the low potential side (low side), one end is connected to a terminal f via a slip ring and a brush (not shown in the drawing), and the other end is grounded. A switching element 106 of a control device 108 is connected to the high potential side (high side) of a load (field coil 102), one end is connected to a rectifier 103 or a battery 120, and the other end is grounded via a (reverse direction) reflux diode 104.
As is apparent from FIG. 13 and FIG. 14, there are two types of the electrical configuration positions of the field coils of the rotors of the generators; and the known control devices 108 for the vehicle AC generators are different devices from each other to correspond to the generators 100 shown in FIG. 13 and FIG. 14. That is, there are two types: as shown in FIG. 13, a low side type where the switching element 105 in which ON/OFF control is to be performed is arranged on the low potential side (low side) of the load (field coil 102); and, as shown in FIG. 14, a high side type where the switching element 106 in which ON/OFF control is to be performed is arranged on the high potential side (high side) of the load (field coil 102). Characteristics of the respective types are as follows. In the low side type, a drive circuit configuration of the switching element 105 is simple and can be reduced in cost and size. In the high side type, a voltage is not applied to the field coil 102 during stopping; therefore, the influence of electrolytic corrosion can be reduced and high reliability can be obtained.
Therefore, although the roles of the control devices for the vehicle AC generators are the same, there are two types of the electrical configuration positions of the field coils of the rotors of the generators; and therefore, there is a problem in that development, design, evaluation, production, and administration for two types of the control devices (chips) have to be made. More particularly, the development and the evaluation demand an investment of tens of millions of yens; and thus, preparation for two types of the control devices of the vehicle AC generators places a considerably large burden on manufacturers of the vehicle AC generator system.